Modern requirements for a computer system may require that a computer be utilized to run several operating environments, or operating systems, at once. In a typical embodiment, a single logically partitioned computer can run a plurality of operating systems in a corresponding plurality of logical partitions. Each operating system resides in its own logical partition, with each logical partition allocated a part of a processor, an entire processor, or multiple processors from the computer. Additionally, a portion of the computer's memory is allocated to each logical partition. All of the logical partitions are under the control of a partition manager. The partition manager is typically a part of the system firmware and manages the allocation of resources to the operating systems and logical partitions.
It may be desirable in some logically partitioned computers to support the migration of a logical partition to a different logically partitioned computer. This process is generally referred to as “partition migration.” A partition migration may be in response to a logical partition failure, operating system failure, optimization plan, user request, or application request. A typical partition migration will suspend user access to the logical partition, then migrate the data and state of a source logical partition on a source computer to a target logical partition on a target computer. User access and control of the target logical partition is granted only after it has been migrated.
The time required to complete a migration, however, can be problematic, particularly in high availability and high performance systems where any downtime is considered highly undesirable. More complex logical partitions may span multiple processors and multiple terabytes of memory, and migrations of such partitions may take hours to complete, and even on smaller partitions that span a single processor and limited memory, partition migration may take still interrupt user access for several minutes or more. It is desirable that partition migration interruption be as “invisible” as possible to users with minimal interruption of user access, so a continuing need exists in the art for a manner of minimizing interruption of user access resulting from partition migrations.
Significant interruption issues may also occur when two or more logical partitions need to be migrated. A typical partition migration will transfer the data of two or more logical partitions sequentially, rather than concurrently. A typical partition migration may suspend access of each user to each of the logical partitions to be migrated while each logical partition is separately migrated. As a result, user access is often impacted to an even greater extent when multiple logical partitions need to be migrated.
Consequently, there is a continuing need for improving logical partition migration and minimizing the user interruption resulting therefrom.